Wasps built nest in bird box now starting to build outside of it how big will it get?

I'm no expert but we have a wasp nest in a bird box on the side of our house and it's now extended outside of the hole. After doing some research we've unfortunately discovered that they will just keep on building, covering the bird box until it's a reasonably large nest. We're getting someone to remove it now before it gets any bigger and poses a threat to our other animals and children.